Janet McCabe, the agency's assistant administrator, said Tuesday that the EPA has already obtained a range of vehicles for testing purposes and that its enforcement staff is working as quickly as possible to determine whether other automakers are gaming emission results.

"That's another detail we'd rather be obscure about, so that we can make sure people don't know what we're doing."

For now, she said the agency is focused on diesel vehicles. But the scope of the new examinations could broaden to include gasoline-powered cars. The renewed efforts could include more light-duty vehicles or focus on heavy-duty trucks. The testing procedures could use dynamometers or portable emissions equipment. Right now, pretty much everything is a possibility.

"We're going to become unpredictable, we're upping our game and we're going to use the whole range of technology that we have," she said.

That technology now includes a heavy-duty truck chassis dynamometer at the EPA's national Vehicle and Fuel Emissions Laboratory in Ann Arbor, MI. Officials unveiled the $3 million piece of equipment Tuesday and hailed it as the first of its kind in North America. A Freightliner Super Truck, which boosted its fuel efficiency to 12 miles per gallon with the help of a $40 million federal grant, rolled onto the dynamometer in a ribbon-cutting ceremony Tuesday.

McCabe said the new dynamometer will allow the EPA to assess the performance of the entire truck – not just its engine – and help engineers test 18-wheel tractor trailers measure, hydrocarbons, greenhouse gases, carbon monoxide and more.

In the past, it took about a week for engineers to remove an engine from a truck and prep it for testing. With the new equipment, drivers can open a garage door and drive the rigs straight onto the dynamometer. A wealth of new, real-time data will be helpful as the EPA works with the National Highway Traffic Safety Administration in planning for the second phase of the government's greenhouse gas emission and fuel-efficiency standards for medium and heavy-duty engines and vehicles – a process now underway.

While there's been a crush of attention on Volkswagen's scheming to circumvent emissions test, in the real world, it's these medium and heavy-duty trucks that are the bigger polluters. EPA emission models show nitrogen oxide from light-duty diesel cars and trucks contributes less than 0.1 percent of NOx pollution from on-road vehicles. Roughly 40 percent of NOx emissions come from heavy-duty diesel trucks, and the remainder comes from gasoline vehicles.

"We're going to become unpredictable, we're upping our game and we're going to use the whole range of technology that we have."

The agency's Ann Arbor facility encompasses roughly 200,000 square feet of space and employs 300 people. In its laboratories, engineers test not only vehicles, but also fuels for engines used in everything from lawnmowers to ocean liners. But testing vehicles for emissions and calculating fuel efficiency numbers that wind up on the window stickers of new cars is the most well-known aspect of the work done there.

David Haugen, director of the agency's Testing and Advanced Technology Division, said the EPA tests about 15 to 20 percent of all new vehicles sold in the domestic fleet, while the remaining percentage are tested by automakers, who then submit detailed results to the agency. But in the aftermath of Volkswagen, the percentage tested at the NVFEL could rise. McCabe kept those plans – along with many others – under wraps Tuesday, but acknowledged that was a possibility.

"That's another detail we'd rather be obscure about, so that we can make sure people don't know what we're doing," she said.

Traditionally, the EPA has used the bulk of its portable emissions measurement systems (PEMS) for testing trucks. With the heavy-duty dynamometer now functioning, there's a possibility more of the agency's 23 portable units will be shifted to evaluating light-duty vehicles, but again, McCabe didn't detail those plans.

One thing the EPA won't be doing is drastically changing its procedures in the hunt for cheaters. Volkswagen "defeat device" used to circumvent the emission tests was, more accurately, an algorithm located in software that governs engine performance. The EPA won't be searching through millions of lines of code to find cheaters; it's going to look for emissions discrepancies. In that sense, it will continue looking for the symptoms of cheating, but not the source.

"Our focus is on what's coming out of the tailpipe," McCabe said, "which is how our standards are set and what the cars need to be measured up against."

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